The present invention relates to a multi-articulated robot, and more particularly to a structure of an articulated portion of rotatable arms.
In general, in an articulated robot of this type a plurality of rotatable arms are supported in a linked manner to a base of the robot. Also, the robot is provided with a work head at a forward end of the linked arms. In order to rotate the work head, a rotatable work shaft must be provided at the forward end of the arms and be supplied with a rotatational torque from the robot side.
If a drive source for rotatingly driving the work shaft is provided on the arms, the gravitational force of the drive source acts on the arms as loads. Therefore, there is a restriction in rotating or swivelling the arms at a high speed. Also, a large inertia would be generated so that it is very difficult to position the work head exactly at a desired location.
Accordingly, usually, the drive source of the work shaft is mounted on the base side of the articulated robot. The rotational torque of the drive source is transmitted through an interior of the arms or timing belts, located below the arms, and through a pulley provided at an intermediate position of an articulation shaft supported at both ends.
However, for the purposes of replacing the timing belt by new one, the belt used in the conventional robot is not of the endless type but of the joint type such as turn buckle belt. The joint type belt is laid around pulleys each having a shaft supported at both ends. For this reason, the transmission of rotation is impossible in a range where the joint is in abutment with the pulley. It is impossible to continuously transmit the rotation.
In order to solve the above-noted problem, if the articulation portions are dismounted for the belt replacement or the shaft of each articulation portion is of the cantilever type to open on one side, it is possible to use an endless belt. However, the dismounting operation is intricate and needs a very skillful work, which is unsuitable for the belt replacement. Also, the cantilever type support causes a fluctuation of the shaft and is inferior in stability of the structure.